Workers remove ledge at Exit 8 on Interstate 89 in Montpelier this week. Twenty years after former Gov. Howard Dean vowed to end unneeded ledge removal work on interstate highways, crews are preparing to blast ledge at the exit in Montpelier.

MONTPELIER — The blasting phase of Vermont’s latest ledge removal project to reduce the risk of rocks falling onto roadways will force motorists traveling north from Montpelier to find another way onto Interstate 89.

The northbound on-ramp of exit 8 is scheduled to close Thursday for a month so that the rock ledge can be removed with explosives as part of a $1.5 million project, which has been under way for several weeks, said Vermont Transportation Agency Project Manager Ken Robie.

“The inside of that ramp, because of the angle of the rock and the way it’s fractured you can’t do it an easier way or a lighter way,” Robie said of using explosives. “So they are going to go in and drill and blast and knock that back to a safer angle.”

Workers will also remove vegetation, which can loosen rocks, from ledges on both sides of the interchange and pry rocks off with heavy equipment and by hand. Robie warned that the methods could change.

“These are kind of dynamic projects. Until you get into it you sometimes don’t know what the treatment is going to be,” Robie said.

There are about 3,000 rock faces along Vermont roadways, including about 500 along state highways that will have to be treated at some point, Robie said.

While there was a public push 20 years ago to end ledge removal projects of rock outcroppings between lanes, Deputy Transportation Secretary Sue Minter said that work is now focused on areas believed to pose a risk of rock falls onto the highway.

“There are a whole lot of possible incidents waiting to happen,” Minter said.

Other recent ledge projects include the northbound lane of I-89 in the Jonesville section of Richmond, Berlin, just south of the Montpelier exit, and an emergency project in Barre after a rock fell into the roadway. There have also been projects at various locations on Interstate 91 and other state routes.